Install Ubuntu Release Upgrader on an older system.
Connect to an older Ubuntu instance.
$ ssh example.org -l mgmt
Welcome to Ubuntu 20.04.4 LTS (GNU/Linux 5.4.0 x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage Last login: Wed Apr 27 16:25:14 2022 from 137.11.134.19
Inspect operating system details.
$ lsb_release -a
No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 20.04.4 LTS Release: 20.04 Codename: focal
Try to check if a new distribution release is available to determine that the Ubuntu Release Upgrader is not installed.
$ do-release-upgrade --check-dist-upgrade-only --devel-release
-bash: do-release-upgrade: command not found
Install ubuntu-release-upgrader-core package.
$ sudo apt install ubuntu-release-upgrader-core
Reading package lists... Done Building dependency tree Reading state information... Done The following additional packages will be installed: iso-codes python-apt-common python3-apt python3-distro-info python3-distupgrade python3-update-manager Suggested packages: isoquery python3-apt-dbg python-apt-doc python3-launchpadlib The following NEW packages will be installed: iso-codes python-apt-common python3-apt python3-distro-info python3-distupgrade python3-update-manager ubuntu-release-upgrader-core 0 upgraded, 7 newly installed, 0 to remove and 0 not upgraded. Need to get 3038 kB of archives. After this operation, 22.3 MB of additional disk space will be used. Do you want to continue? [Y/n] y Get:1 http://archive.ubuntu.com/ubuntu focal/main amd64 iso-codes all 4.4-1 [2695 kB] Get:2 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 python-apt-common all 2.0.0ubuntu0.20.04.7 [17.1 kB] Get:3 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 python3-apt amd64 2.0.0ubuntu0.20.04.7 [154 kB] Get:4 http://archive.ubuntu.com/ubuntu focal/main amd64 python3-distro-info all 0.23ubuntu1 [5924 B] Get:5 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 python3-update-manager all 1:20.04.10.10 [38.1 kB] Get:6 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 python3-distupgrade all 1:20.04.38 [104 kB] Get:7 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 ubuntu-release-upgrader-core all 1:20.04.38 [24.3 kB] Fetched 3038 kB in 1s (2704 kB/s) Selecting previously unselected package iso-codes. (Reading database ... 27217 files and directories currently installed.) Preparing to unpack .../0-iso-codes_4.4-1_all.deb ... Unpacking iso-codes (4.4-1) ... Selecting previously unselected package python-apt-common. Preparing to unpack .../1-python-apt-common_2.0.0ubuntu0.20.04.7_all.deb ... Unpacking python-apt-common (2.0.0ubuntu0.20.04.7) ... Selecting previously unselected package python3-apt. Preparing to unpack .../2-python3-apt_2.0.0ubuntu0.20.04.7_amd64.deb ... Unpacking python3-apt (2.0.0ubuntu0.20.04.7) ... Selecting previously unselected package python3-distro-info. Preparing to unpack .../3-python3-distro-info_0.23ubuntu1_all.deb ... Unpacking python3-distro-info (0.23ubuntu1) ... Selecting previously unselected package python3-update-manager. Preparing to unpack .../4-python3-update-manager_1%3a20.04.10.10_all.deb ... Unpacking python3-update-manager (1:20.04.10.10) ... Selecting previously unselected package python3-distupgrade. Preparing to unpack .../5-python3-distupgrade_1%3a20.04.38_all.deb ... Unpacking python3-distupgrade (1:20.04.38) ... Selecting previously unselected package ubuntu-release-upgrader-core. Preparing to unpack .../6-ubuntu-release-upgrader-core_1%3a20.04.38_all.deb ... Unpacking ubuntu-release-upgrader-core (1:20.04.38) ... Setting up python-apt-common (2.0.0ubuntu0.20.04.7) ... Setting up python3-distro-info (0.23ubuntu1) ... Setting up iso-codes (4.4-1) ... Setting up python3-apt (2.0.0ubuntu0.20.04.7) ... Setting up python3-update-manager (1:20.04.10.10) ... Setting up python3-distupgrade (1:20.04.38) ... Setting up ubuntu-release-upgrader-core (1:20.04.38) ... Processing triggers for man-db (2.9.1-1) ...
Inspect available releases.
$ do-release-upgrade --check-dist-upgrade-only --devel-release
Checking for a new Ubuntu release New release '22.04' available. Run 'do-release-upgrade' to upgrade to it.
$ do-release-upgrade --check-dist-upgrade-only
Checking for a new Ubuntu release New release '21.10' available. Run 'do-release-upgrade' to upgrade to it.
Start release upgrade.
$ sudo do-release-upgrade --devel-release
Additional notes
The Ubuntu Release Upgrader requires the Python 3 interface to D-Bus which can be missing in this case.
ModuleNotFoundError: No module named 'dbus'
Install python3-dbus package and retry operation.
$ sudo apt-get install python3-dbus